Apparatus and method for smooth audio scaling

Abstract

Apparatus and method for scaling volume for a multimedia computer system are disclosed. A volume control algorithm, in association with the computer system hardware, increases or decreases the perceived volume over time. The increase or decrease in volume being scaled to correspond to the logarithmic nature of perceived audio transmissions. Thus, fifty percent of the maximum on a given volume scale corresponds to a human perceived half volume output.

Having thus described our invention, what we claim as new, and desire to secure by Letters Patent is: 
     
       1. An apparatus for controlling volume of a digital audio signal comprising: digital signal processor means for translating a first linear volume value to a first logarithmically scaled volume value of the digital audio signal at a first time, the translating means comprising:   means for selecting a mask value from a table of calculated mask values according to a remainder from a division operation;   means for shifting the selected mask value according to an integer from the division operation;   a digital signal processor means for multiplying the first logarithmically scaled volume value to the digital audio signal at the first time; and   digital to analog converter means for converting the multiplied digital audio signal into an audio signal.   
     
     
       2. The apparatus as recited in claim 1 further comprising: means for receiving a desired linear volume value and a desired ramp rate;   means for calculating a linear volume change per unit of time according to the first and desired linear volume values and the desired ramp rate; and,   means for updating a current linear volume after a unit of time has elapsed.   
     
     
       3. The apparatus as recited in claim 2 wherein the translating digital signal processor means translates the current linear volume value to a current logarithmically scaled volume value of the digital audio signal at a current time, the multiplying digital signal processor means multiplies the current logarithmically scaled volume value to the digital audio signal at the current time and the digital to analog converter means converts the multiplied digital audio signal at the current time into an audio signal. 
     
     
       4. The apparatus as recited in claim 2 wherein the desired linear volume and desired ramp rate are received from an application resident in a memory of a computer. 
     
     
       5. A method for controlling volume of a digital audio signal comprising the steps of: translating a first linear volume value to a first logarithmically scaled volume value of the digital audio signal at a first time, the translating step comprising the steps of:   selecting a mask value from a table of calculated mask values according to a remainder from a division operation;   shifting the selected mask value according to an integer from the division operation;   multiplying the first logarithmically scaled volume value to the digital audio signal at the first time; and,   converting the multiplied digital audio signal into an audio signal.   
     
     
       6. The method as recited in claim 5 further comprising: receiving a desired linear volume value and a desired ramp rate;   calculating a linear volume change per unit of time according to the first and desired linear volume values and the desired ramp rate; and,   updating a current linear volume after a unit of time has elapsed.   
     
     
       7. The method as recited in claim 6 wherein the current linear volume is translated to a current logarithmically scaled volume value of the digital audio signal at a current time, the current logarithmically scaled volume value is multiplied to the digital audio signal at the current time and the multiplied digital audio signal at the current time is converted into an audio signal. 
     
     
       8. The method as recited in claim 6 wherein the desired linear volume and desired ramp rate are received from an application resident in a memory of a computer. 
     
     
       9. A control element for directing the operation of a computer comprising storage for retaining signals recognizable by the computer for controlling the operation thereof, the signals comprising; a digital audio signal comprising a sequence of digitized audio samples, each audio sample associated with one of a sequence of time intervals;   a first linear volume value associated with a first time interval within the sequence of time intervals;   a desired linear volume value associated with a second time interval within the sequence of time intervals;   a desired ramp rate to smoothly step a current linear volume value from the first linear volume value to the desired linear volume value, the current linear volume value associated with a current time interval; and,   a current logarithmic volume value which is calculated by dividing the linear value, selecting a mask value form a table of calculated mask values according to a remainder from the division operation and shifting the selected mask value according to an integer form the division operation;   so that the audio sample associated with the current time interval is multiplied by the current logarithmic volume value and converted into an analog audio signal by a digital to analog converter.